Low energy electron accelerators application - ICC

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10 Nov 2011 ... Electron accelerators in the range 10 – 25 MeV in most cases are also built as RF linear accelerator with max beam power up to tens kW and ...
LOW ENERGY ELECTRON ACCELERATORS APPLICATION V. Shvedunov Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University 10 November 2011

Electron accelerators in the range 0.5 – 100 MeV Some applications use bremsstrahlung (X-rays) radiation, some – electron beam. For X-rays

I = I 0 exp(− µx ) For electrons

Different mechanisms of radiation interaction with matter are used for different applications - at level of molecules, atoms, nuclei

ACCELERATORS

Electron accelerators in the range 0.5 – 5 MeV in most cases are built as direct current accelerator with max beam power up to several hundred kW and efficiency 80-90%.

Basic suppliers: Nissin High Voltage Ion Beam applications Budker Institute Efremov Institute

Examples of electron accelerators in the range 0.5 – 5 MeV

Nissin HV 5 MeV,150 kW ELV (Budker Institute) 0.2 – 2.5 MeV, up to 500 kW

Examples of electron accelerators in the range 0.5 – 5 MeV DYNAMITRON (IBA)

Electron accelerators in the range 5 – 10 MeV in most cases are built as RF standing wave or traveling wave linear accelerator (linac) with max beam power up to hundred kW and efficiency 20-30%.

Traveling Wave (TW) RF waveguide Standing Wave (SW)

CUT VIEW OF STANDING WAVE ACCELERATING STRUCTURES

Side coupled

On-axis coupled

Examples of electron linacs in the range 5 – 10 MeV

TitanBeta SW linac 10 MeV, 25 kW Mitsubishi Heavy Industries TW linac 10 MeV, 25 kW

IMPELA SW linac 10 MeV, 50 kW

SureBeam SW linac 5 MeV,100 kW

Example of electron accelerator in the range 5 – 10 MeV - recirculating RF cavity accelerator

Rhodotron, IBA 5 -10 MeV up to 700 kW

In some applications cheap betatrons are used in the range 3 – 25 MeV

Betatron principle

10 MeV betatron for IORT (Tomsk)

3-7.5 MeV betatrons (Tomsk)

Electron accelerators in the range 10 – 25 MeV in most cases are also built as RF linear accelerator with max beam power up to tens kW and efficiency 20-30%. In some cases microtrons and betatrons are used.

Microtron

Examples of electron accelerators in the range 10 – 25 MeV

MEVEX, Canada, 35 MeV linac for isotopes production

Varian 25 MeV Clinac

20 MeV circular microtron, Indore, India

Electron accelerators in the range 25 – 100 MeV in most cases are built as multisections RF linear accelerator or as race-track microtron (RTM).

Examples of electron accelerators in the range 25 - 100 MeV

Scanditronix medical RTM MM-50

Danfysik 53 MeV RTM

Research Instruments 100 MeV linac

APPLICATIONS

Electron accelerators application for material processing, sterilization, desinsection Chemical and biological effects at molecules level are produces by ~eV energy electrons. Initial high electrons energy is required to penetrate inside the material. Productivity:

∆m Pbeam =η ∆t D

To increase penetration electron energy can be converted to X-rays energy at bremsstrahlung target, but efficiency of conversion in energy range below 10 MeV is below 10%, so high power electron beams are required.

Dose requirements for various radiation effects and productivity for 10 kW electron beam power 1 Gy = 1 J/kg •

Radiation effect

Dose requirements

Productivity



Sprout inhibition (potatoes, onions)

100-200 Gy

~200-100 tons/hour



Insect control (grains, fruits)

250-500 Gy

~80-40 tons/hour



Fungi and mould control

1-3 kGy

~10-3 tons/hour



Bacterial spore sterilization

10-30 kGy

~2-0.7 tons/hour



Polymerization of monomers

10-50 kGy

~2-0.4 tons/hour



Anthrax killing

50-100 kGy

~400-200 kg/hour



Modification of polymers

50-250 kGy

~400-80 kg/hour



Degradation of cellulose materials

100-500 kGy

~200-40 kg/hour



Topaz coloring

10-200 MGy

~1-0.05 kg/hour

Irradiation facility based on “Dynamitron” (IBA)

Rated Voltage

Rated beam current

550 keV

70/100/160 mA

800 keV

70/100/160 mA

1 MeV

60/100 mA

1.5 MeV

40/65 mA

2.5 MeV

40 mA

3 MeV

34/50 mA

4.5 MeV

20/34 mA

5 MeV

10/20/34 mA

Structure of 10 MeV/25 kW irradiation facility

http://www.mhi.co.jp/hmw/melbis/structure-e.html

SINP MSU experience in design, construction and application of electron accelerators for radiation technologies

SINP MSU 60 KW, 1.2 MEV COMPACT CW LINAC FOR RADIATION TECHNOLOGIES

OneSection

TwoSections

Beam energy

0.6 MeV

1.2 MeV

Beam current

0 to 50 mA

0 to 50 mA

Maximum beam power

30 kW

60 kW

Length

0.8 m

1.3 m

Gun/klystron high voltage

15 kV

15 kV

Plug power consumption

~75 kW

~150 kW

Electrical efficiency

~40%

~40%

SOME CURRENT APPLICATIONS OF 1.2 MEV COMPACT CW LINAC 1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. Source of high dose rate X-rays radiation 3. R&D for radiation technologies

Thermo shrinkable polyethylene film dimensions decrease after different doses. Optimal dose 120 kGy.

Intensive bremsstrahlung X-rays source (30 Gy/s at average energy 300 keV)

SINP MSU COMPACT CW LINEAR ACCELERATOR FOR RADIATION TECHNOLOGIES WITH LOCAL RADIATION SHIELDING CWL-1-25 Under construction. Beam energy Average beam current Average beam power Operating frequency Klystron average power Wall plug efficiency Beam scanning width Accelerator dimensions

1 MeV 25 mA 25 kW 2450 MHz 50 kW 30% 80 cm 470 x 784 x 1375 mm1)

1)Without output horn and power supply

Accelerator is able to provide operation of thermo shrinkable polyethylene film facility with productivity up to 10000 tons/year

SINP MSU 10 MeV TECHNOLOGICAL LINAC

Beam energy Pulsed beam current Average beam power Operating frequency Klystron pulsed power Klystron average power Wall plug efficiency Beam scanning width

10 MeV 430 mA 15 kW 2856 MHz 6 MW 25 kW 20% 80 cm

Energy spectrum, beam image and beam profile

0.08 0.07 0.06

0.04 0.03 0.02 0.01

180 160

0 -0.01

140

0

2

4

6

8

10

12

120 100

E (МэВ)

I

I(45)/I(0)

0.05

80 60 40 20 0 -3

-2

-1

0 y (mm)

1

2

3

SOME CURRENT APPLICATIONS OF 10 MEV LINAC

1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. R&D for radiation technologies

Example of possible application – gemstones colorization

SINP MSU 10 MeV TECHNOLOGICAL LINAC Proposal

Pulsed Linear Accelerator PLA-10-15H Beam energy Pulsed beam current Average beam power Operating frequency Klystron pulsed power Klystron average power Wall plug efficiency Beam scanning width Accelerator dimensions 1)Without

output horn and power supply

Pulsed Linear Accelerator PLA-10-15V 10 MeV 430 mA 15 kW 2856 MHz 6 MW 25 kW 20% 80 cm 470 x 784 x 1375 mm1)

CARGO INSPECTION AND RADIOGRAPHY X-rays produced by electrons at bremsstrahlung target are used in both applications. X-rays are attenuated by inspected object and registered by X-rays detectors or by film.

Basic processes responsible for X-rays attenuation

Cargo inspection. 40 mln. sea containers per year move in the word.

Cargo inspection - goals. 1. Detection of contraband. 2. Detection of fissile and radioactive materials. 3. Detection of explosive and drugs. Different approaches are necessary for each problem, but in all cases electron accelerators are used or can be used.

Typical dimensions.

Required speed of development: 0.5 m/s

Main components of cargo inspection complex

Basic companies providing equipment and complexes for cargo inspection are: Varian Medical Systems (USA) Smiths Detection (UK) Nuctech (China) L-3 (USA) Rapiscan (USA) SAIC (USA) AS&E (USA) ………….. Several other companies are working in this direction

Single energy bremsstrahlung X-rays do not permit to evaluate atomic number and can produce only gray picture 10.00

Bremsstrahlung spectrum

1.00

2

µ/ρ (cm /g)

Uranium

Iron

Co 60

0.10 Nitrogen

0.01 0.1

1.0 E (MeV)

10.0

Dual energy bremsstrahlung X-rays do permit to evaluate atomic number and can produce color picture 10.00

Bremsstrahlung spectra

1.00

2

µ/ρ (cm /g)

Uranium

Iron 0.10 Nitrogen

0.01 0.1

1.0 E (MeV)

10.0

The most widely used are X-ray sources from Varian Medical Systems. Linatron-Mi –is dual energy X-Ray source fed by magnetron

Nuctech (China) – also produces 6/9 MeV dual energy X-Ray source fed by magnetron

Design by SINP MSU team of 3/6 MeV linac with interlaced energies for cargo inspection X-rays head

Beam energy Dose rate at 1 m Operating frequency Pulse repetition frequency Accelerator dimensions Accelerator weignt 1)Including

Control console

local radiation shielding

3.5/6 MeV 0.2 – 2 Gy/min 2856 MHz 50 – 400 Hz 1000x600x900 mm 900 kg1)

Energy spectrum in interlaced energies mode 600 500

Iav (nA)

400 300 200 100 0 0

1

2

3

4

5

6

7

8

E (MeV)

Low

High

Beam spots diameters are well below 2 mm

Scale: 1 square= 1 1 mm

ACCELERATOR WITH FAST MAGNETIC ENERGY SWITCHING FOR CARGO INSPECTION (PROPOSAL)

RTM Parameters Beam energies

3.5, 6, 9 MeV

Operating frequency

2998 MHz

End magnets field

0.63 T

Injection energy

25 keV

Pulsed RF power

39Ca + n

+ γ --> 207Pb + n

Photo activation technique –method of elemental analysis – using photonuclear reactions.

Nuclei level structure is unique fingerprints permitting to detect specific elements in very low quantities Level structure of gold isotope 196Au. Level with energy 595.66 keV has half life period 9.6 h. 196Au

can be produced in this isomeric state via photoneutron reaction at stable isotope 197Au. In this way gold content in ore can be defined with high sensitivity - better than 1 g/ton

Photo activation technique

Photo activation technique

Gamma ray spectrum obtained with Ge detector

Accelerators for photo activation technique Electron beam parameters: Beam energy from ~ 10 MeV to ~30 MeV Beam average current from ~100 µA-1 mA Conversion to bremsstrahlung X-rays

Isotopes production Most isotopes for medicine are produced now with cyclotrons, proton linacs and with reactors. List of radioactive isotopes used in medicine for treatment and for producing images includes more than 100 nuclei with life time from several years, e.g. 60Co, to several seconds, e.g. 191mIr.

Photonuclear reactions offer another way for isotope production. Electron accelerator is several times cheaper than cyclotron

PET isotopes – short living isotopes for positron emission tomography 11C (20.4 min), 13N (10.0 min), 15O (2.0 min), 18F (109.8 min)

can be produced via (γ,n) reaction on target nuclei 12C, 14N, 16O, 19F

Cross section of (γ,n) reaction is 10-100 lower than cross section of reactions with heavy charged particles obtained with cyclotron. However for photonuclear reactions much more thick target can be used, so total isotope yield can be sufficiently high.

Estimations for PET isotopes yields with cyclotron and RTM Isotope

Accelerator

Reaction

Target

Saturation Yields

11C

70/35 MeV RTM

12C(γ,n)11C

Graphite -- Diamond

2.6/3.9 Ci -- 4.8/7.1 Ci

11 MeV Cyclotron

14N(p,α)11C

N2 / 0.5-1% O2

3.0 Ci

70/35 MeV RTM

14N(γ,n)13N

Melamine (C3H3N3)

1.2/1.6 Ci

11 MeV Cyclotron

16O(p,α)13N

5mM Water&Ethanol

100 mCi

70/35 MeV RTM

16O(γ,n)15O

Water

3.2/2.5 Ci

11 MeV Cyclotron

15N(p,n)15O

N2 / 2.5% O2

760 mCi

70/35 MeV RTM

19F(γ,n)18F

Perfluorocarbon or SF6 gas

2.2/3.0 Ci

11 MeV Cyclotron

18O(p,n)18F

H218O or18O2

1-3 Ci

13N

15O

18F

Radiochemistry can not be applied for (γ,n) reaction products – isotope with the same as target chemical properties is produced. How to extract? For example, use of thin powder and pick-up recoil nuclei with gas stream.

99mTc

(the daughter nucleus of 99Mo) is most used isotope in medical imagine. It is now obtained with nuclear reactor. Can be obtained in 100Mo(γ,n)99Mo reaction. Method was experimentally verified. Production of very pure 123I was demonstrated with electron accelerators at several centers. Reaction 124Xe (γ,n)123Xe123I was used. Electron accelerator for medical isotopes production: Beam energy from ~ 25 MeV to ~40 MeV Beam average current from ~100 µA to ~200 µA Conversion to bremsstrahlung X-rays

Explosive detection with photonuclear reactions Original idea of L. Alvarez Tested by Trower W.P., NIM B79 (1993) 589 The most effective method of concealed explosive search till now is odorant method - dogs. However explosive can be detected by detecting its main constituents - nitrogen and oxygen. Anomaly concentration of nitrogen and oxygen in certain proportion means high probability of explosive presence.

β decaying radionuclei photoproduced on stable isotopes with abundance >1 % resulting in three or fewer nucleons.

Only photonuclear reactions on carbon, nitrogen and oxygen for beam energy below 70 MeV can produce residual nuclei with half life between 10 and 100 ms.

Explosive detection with photonuclear reactions Lebedev Institute Max 70 MeV electron accelerator

Detector

Scanned electron beam

Moving object

Explosive detection steps 1. Irradiate during 5-10 µs specific portion of object by X-ray radiation generated by electron beam at large (~object dimensions) bremsstrahlung target. 2. Get decay curve within ~ 10-20 ms by mean of registration of secondary X-rays, produced by positrons, emitted by residual nuclei. 3. Go to the next part of object Irradiation of the same object part with different electron energy can be used to distinguish between C, N and O. For the same goal different secondary X-rays registration threshold energy can be used.

Decay curves measured for different substances

Melamine

Room air

Example of explosive detection

No explosive

Semtex, 125 g

Electron accelerator for explosive detection technique: Beam energy from ~25 to ~70 MeV Pulsed current ~20-50 mA Pulse duration ~5-10 µs Pulse repetition rate 10-50 Hz Conversion to bremsstrahlung X-rays

SINP MSU experience in design, construction and application of electron accelerators for activation analysis, isotopes production and explosive detection

SINP MSU 70 MeV PULSED RACE TRACK MICROTRON WITH RARE-EARTH PERMANENT MAGNETS

Innovations: -large ~1 T rare-earth permanent end magnets - rectangular accelerating structure with RF quadrupole focusing - electron beam phase shifter - rare-earth permanent magnet compact quadrupole triplets - self excitation RF system

Injection energy

48 keV

Energy gain

4.8 MeV / orbit

Orbits

14

Output energy

14.8 - 68.3 MeV

Output current at 68.3 MeV

10 mA

Orbit circumference increase

1λ/orbit

Operating frequency

2,856 MHz

Klystron power pulsed

6 MW

End magnet field induction

0.963 T

RTM dimensions

2.2x1.8x0.9 m3

A 70 Mev racetrack microtron, V.I. Shvedunov, A.N. Ermakov, I.V. Gribov, E.A. Knapp, G.A. Novikov, N.I. Pakhomov, I.V. Shvedunov, V.S. Skachkov, N.P. Sobenin, W.P. Trower and V.R. Yajlijan, Nucl. Instrum. Meth. A550 (2005)39-53

Photoactivation technique Gamma rays spectrum from Ge detector after irradiation of 197Au with bremsstrahlung from 70 MeV RTM

55 MeV PULSED RACE TRACK MICROTRON AT SINP MSU WITH EXPLOSIVE DETECTION SYSTEM – COLLABORATION WITH LEBEDEV PHYSICAL INSTITUTE

Synchrotron radiation from orbits

Radiation therapy Use of ionizing radiation to kill tumor cells by destroying DNA via complicated physical, chemical and biological processes. Together with tumor cells normal cells on the way of radiation are also killed. Special tactic of irradiation: irradiation from several sides, using special collimators, intraoperative radiation therapy etc.

Cell survival curves

Typical cell survival curves for high LET (densely ionizing) radiation and low LET (sparsely ionizing) radiation. LET – linear energy transfer

Comparison of electrons and X-rays dose-depth dependencies

PPD – percentage depth dose

External X-ray radiation therapy Irradiation by bremsstrahlung radiation produced by 1 - 25 MeV electron beam at special target.

External electron radiation therapy Irradiation by 25 - 50 MeV electron beam scattered by foil via special applicator.

Scanditronix medical RTM MM-50

Stereotactic radiation surgery (SRS) Providing of high dose of X-rays radiation to well localized volume using several radiation sources or single easy movable source. SRS uses dedicated miniature electron accelerator with energy 4-6 MeV, fixed at robotic arm.

CyberKnife - based on 6 MeV X-band linac

Intraoperative radiation therapy (IORT) Providing of high dose to well localized volume using several radiation sources or single easy movable source. Similar to IORT modern SRS uses dedicated miniature electron accelerator with energy 4-6 MeV, fixed at robotic arm.

Betatron Russia

Mobetron USA

Novac7 Italy

Liac Italy

UPC-SINP MSU-CIEMAT collaboration for IORT dedicated 12 MeV race-track microtron

Conclusion Electron beams in the energy range 0.5 – 100 MeV have wide and growing spectrum of applications. There are three distinctly different kind of commercial activity in this field : -accelerator design and construction; -technology development; -facility construction and technology application. Many labs conduct R&D in accelerator physics and only a few private companies manufacture commercial electron accelerators. New accelerator busyness can be successful only with new ideas in accelerator design and application.